1. Technical Field
The present invention relates to a telescopic sight which includes a zoom mechanism which stably maintains a sighting alignment of the telescopic sight and which implements zooming with a light touch.
2. Background Art
Heretofore, in a zoom mechanism of a telescopic sight, in order to transmit turning of a zoom ring disposed at the outside of a lens barrel to a cam tube disposed inside the lens barrel, a groove aperture with a circular arc form has been formed in the lens barrel. This groove aperture is opened in the circular arc form through a broad angle about an optical axis of the telescopic sight (for example, an angle of around 300°). Moreover, this groove aperture is disposed between a zoom lens and an eyepiece lens, and arranged in a direction intersecting the optical axis. Hence, there has been a problem in that the strength at locations of the groove aperture is low when external forces, such as impacts and the like, act on the lens barrel.
A telescopic sight for solving this previous problem is equipped with a zoom mechanism which does not require the broad-angle groove aperture. This sight has been proposed by the present inventor, as shown in FIGS. 6 and 7 (see Japanese Publication No. JP 7281101). In such a telescopic sight 51, a zoom ring 54 is mounted at a tubular body 53 which is joined to a lens barrel 52, and the zoom ring 54 is made rotatable with respect to the lens barrel 52. An annular gear 55 is provided at an inner periphery face of the zoom ring 54, and a circumferential gear 58 is provided at an outer periphery face of a cam tube 56, which is rotatably provided inside the lens barrel 52. Meanwhile, an intermediate gear 57 is rotatably provided in a small hole 59 in the tubular body 53. This intermediate gear 57 is interposed between the annular gear 55 and the circumferential gear 58. Thus, turning of the zoom ring 54 is transmitted via the intermediate gear 57 to the cam tube 56, so as to implement zooming of the telescopic sight 51.